Technical details

A fastening system without additional locking nuts & washers - Due to self-locking mechanism

The key to CONU’s strength and versatility is its design: Due to the angle difference between nut and countersunk hole, plus due to the added serrations on the conical surface, the self-locking mechanism starts and then gets stronger the further the nut is pulled into the countersunk hole. This prevents the joints from ‘self-loosening’. In addition, the counter nut can be tightened and locked without needing a spanner to hold the nut.

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Junker tests prove constant preload

Various vibration tests, including the Junker test (the most demanding vibration test for bolted joints standardised according to DIN 65151), have confirmed that the preload remains almost constant despite strong vibrations and that the loss of preload due to ‘settlements’ is very low, at approx. 15 %.

The tests were carried out in the laboratories of REYHER, NORD-LOCK, HEWI and IMA Dresden.

The CONU nut has also demonstrated that an adequate securing effect can still achieved, even when lower preload (such as 6 kN or 2 kN) are applied.

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Carrying capacity with CONU

The load-bearing capacity of nuts depends on the material hardness and nut thread height. The load-bearing values have been determined via a series of tests conducted on the M 8 sized CONU nut.

Using heat-treated steel with a hardness grade of 220-300 HV, tests have confirmed that the CONU-S with a height of 0.6 x d can reach preload levels that are consistent with, and suitable for grade 8.8 screws and bolts.

In addition, the CONU-L version has been confirmed to be compatible with ISO 898-2 grade 10 mechanical properties and thus suitable for applications requiring grade 10.9 screws or bolts. In order to achieve the full loading-capacity, the end of the screw-thread needs to go beyond the last thread of the CONU nut.